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April 2, 2017 02:16
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问题1:如何重载toString
1.toString是Objects的内部函数，不需要显式继承就可以覆盖，当然显式继承也可以。
参见：http://www.geeksforgeeks.org/overriding-tostring-method-in-java/
问题2:
2.为何重载了toString，println就会去调用它？
参见：http://stackoverflow.com/questions/29318996/the-connection-between-system-out-println-and-tostring-in-java
...calls at first String.valueOf(x) to get the printed object's stri…
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| // file name: Main.java | |
| class Complex { | |
| private double re, im; | |
| public Complex(double re, double im) { | |
| this.re = re; | |
| this.im = im; | |
| } | |
| } | |
| // Driver class to test the Complex class | |
| public class Complex_test1 { | |
| public static void main(String[] args) { | |
| Complex c1 = new Complex(10, 15); | |
| System.out.println(c1); | |
| } | |
| } |
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| // file name: Main.java | |
| class Complex extends Object{ | |
| private double re, im; | |
| public Complex(double re, double im) { | |
| this.re = re; | |
| this.im = im; | |
| } | |
| /* Returns the string representation of this Complex number. | |
| The format of string is "Re + iIm" where Re is real part | |
| and Im is imagenary part.*/ | |
| @Override | |
| public String toString() { | |
| return String.format(re + " + i" + im); | |
| } | |
| } | |
| // Driver class to test the Complex class | |
| public class Complex_test2 { | |
| public static void main(String[] args) { | |
| Complex c1 = new Complex(10, 15); | |
| System.out.println(c1); | |
| } | |
| } |
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